Tetrahydrocannabinols are the active constituents of marijuana (hashish). The major active form, the Δ1-3,4-trans isomer of chemical formula:
known as Δ9-THC, or by the generic name dronabinol, has approved pharmaceutical applications as an anti-emetic, e.g. for enhancing appetite in patients suffering side effects of chemotherapy, suffering from AIDS or anorexia. Its synthesis on a commercial scale presents particular difficulties, however, because the compound possesses several stereoisomeric forms, only one of which, the Δ1-3,4-trans isomer (dronabinol), is significantly active. Synthetic processes which lead to the production of a mixture of stereoisomers require a step of separation of the stereoisomers, which is difficult and tedious and tends to render such a process economically unattractive. Extraction of dronabinol from its natural plant source presents similar difficulties, since other stereoisomers are naturally present.